Twenty-four drift cards, released in 1964 through 1966 in the vicinity of Cape Town and at various locations in the Atlantic Ocean, have been recovered on the coasts of: North and South America, three islands in the South Atlantic, England, France, Nigeria, and Australia. The travel times indicated by 19 of these cards have been used to estimate the mean velocities of the presumed current systems involved. The rate of card recovery and the long distances traveled by the cards have proved conclusively that the solid polythene drift card is durable.
Stander, G. H., L. V. Shannon, and J. A. Campbell. 1969. "Average velocities of some ocean currents as deduced from the recovery of plastic drift cards." Journal of Marine Research 27, (3). https://elischolar.library.yale.edu/journal_of_marine_research/1160